// jpgd.h - C++ class for JPEG decompression.
// Public domain, Rich Geldreich <richgel99@gmail.com>
#ifndef JPEG_DECODER_H
#define JPEG_DECODER_H

#include <stdlib.h>
#include <stdio.h>
#include <setjmp.h>

#ifdef _MSC_VER
#define JPGD_NORETURN __declspec(noreturn)
#elif defined(__GNUC__)
#define JPGD_NORETURN __attribute__((noreturn))
#else
#define JPGD_NORETURN
#endif

namespace jpgd
{
typedef unsigned char uint8;
typedef signed short int16;
typedef unsigned short uint16;
typedef unsigned int uint;
typedef signed int int32;

// Loads a JPEG image from a memory buffer or a file.
// req_comps can be 1 (grayscale), 3 (RGB), or 4 (RGBA).
// On return, width/height will be set to the image's dimensions, and actual_comps will be set to the either 1
// (grayscale) or 3 (RGB). Notes: For more control over where and how the source data is read, see the
// decompress_jpeg_image_from_stream() function below, or call the jpeg_decoder class directly. Requesting a 8 or 32bpp
// image is currently a little faster than 24bpp because the jpeg_decoder class itself currently always unpacks to
// either 8 or 32bpp.
unsigned char *decompress_jpeg_image_from_memory(const unsigned char *pSrc_data, int src_data_size, int *width,
                                                 int *height, int *actual_comps, int req_comps);
unsigned char *decompress_jpeg_image_from_file(const char *pSrc_filename, int *width, int *height, int *actual_comps,
                                               int req_comps);

// Success/failure error codes.
enum jpgd_status
{
    JPGD_SUCCESS = 0,
    JPGD_FAILED = -1,
    JPGD_DONE = 1,
    JPGD_BAD_DHT_COUNTS = -256,
    JPGD_BAD_DHT_INDEX,
    JPGD_BAD_DHT_MARKER,
    JPGD_BAD_DQT_MARKER,
    JPGD_BAD_DQT_TABLE,
    JPGD_BAD_PRECISION,
    JPGD_BAD_HEIGHT,
    JPGD_BAD_WIDTH,
    JPGD_TOO_MANY_COMPONENTS,
    JPGD_BAD_SOF_LENGTH,
    JPGD_BAD_VARIABLE_MARKER,
    JPGD_BAD_DRI_LENGTH,
    JPGD_BAD_SOS_LENGTH,
    JPGD_BAD_SOS_COMP_ID,
    JPGD_W_EXTRA_BYTES_BEFORE_MARKER,
    JPGD_NO_ARITHMITIC_SUPPORT,
    JPGD_UNEXPECTED_MARKER,
    JPGD_NOT_JPEG,
    JPGD_UNSUPPORTED_MARKER,
    JPGD_BAD_DQT_LENGTH,
    JPGD_TOO_MANY_BLOCKS,
    JPGD_UNDEFINED_QUANT_TABLE,
    JPGD_UNDEFINED_HUFF_TABLE,
    JPGD_NOT_SINGLE_SCAN,
    JPGD_UNSUPPORTED_COLORSPACE,
    JPGD_UNSUPPORTED_SAMP_FACTORS,
    JPGD_DECODE_ERROR,
    JPGD_BAD_RESTART_MARKER,
    JPGD_ASSERTION_ERROR,
    JPGD_BAD_SOS_SPECTRAL,
    JPGD_BAD_SOS_SUCCESSIVE,
    JPGD_STREAM_READ,
    JPGD_NOTENOUGHMEM
};

// Input stream interface.
// Derive from this class to read input data from sources other than files or memory. Set m_eof_flag to true when no
// more data is available. The decoder is rather greedy: it will keep on calling this method until its internal input
// buffer is full, or until the EOF flag is set. It the input stream contains data after the JPEG stream's EOI (end of
// image) marker it will probably be pulled into the internal buffer. Call the get_total_bytes_read() method to
// determine the actual size of the JPEG stream after successful decoding.
class jpeg_decoder_stream
{
public:
    jpeg_decoder_stream() {}
    virtual ~jpeg_decoder_stream() {}

    // The read() method is called when the internal input buffer is empty.
    // Parameters:
    // pBuf - input buffer
    // max_bytes_to_read - maximum bytes that can be written to pBuf
    // pEOF_flag - set this to true if at end of stream (no more bytes remaining)
    // Returns -1 on error, otherwise return the number of bytes actually written to the buffer (which may be 0).
    // Notes: This method will be called in a loop until you set *pEOF_flag to true or the internal buffer is full.
    virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag) = 0;
};

// stdio FILE stream class.
class jpeg_decoder_file_stream : public jpeg_decoder_stream
{
    jpeg_decoder_file_stream(const jpeg_decoder_file_stream &);
    jpeg_decoder_file_stream &operator=(const jpeg_decoder_file_stream &);

    FILE *m_pFile;
    bool m_eof_flag, m_error_flag;

public:
    jpeg_decoder_file_stream();
    virtual ~jpeg_decoder_file_stream();

    bool open(const char *Pfilename);
    void close();

    virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag);
};

// Memory stream class.
class jpeg_decoder_mem_stream : public jpeg_decoder_stream
{
    const uint8 *m_pSrc_data;
    uint m_ofs, m_size;

public:
    jpeg_decoder_mem_stream()
        : m_pSrc_data(NULL)
        , m_ofs(0)
        , m_size(0)
    {
    }
    jpeg_decoder_mem_stream(const uint8 *pSrc_data, uint size)
        : m_pSrc_data(pSrc_data)
        , m_ofs(0)
        , m_size(size)
    {
    }

    virtual ~jpeg_decoder_mem_stream() {}

    bool open(const uint8 *pSrc_data, uint size);
    void close()
    {
        m_pSrc_data = NULL;
        m_ofs = 0;
        m_size = 0;
    }

    virtual int read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag);
};

// Loads JPEG file from a jpeg_decoder_stream.
unsigned char *decompress_jpeg_image_from_stream(jpeg_decoder_stream *pStream, int *width, int *height,
                                                 int *actual_comps, int req_comps);

enum
{
    JPGD_IN_BUF_SIZE = 8192,
    JPGD_MAX_BLOCKS_PER_MCU = 10,
    JPGD_MAX_HUFF_TABLES = 8,
    JPGD_MAX_QUANT_TABLES = 4,
    JPGD_MAX_COMPONENTS = 4,
    JPGD_MAX_COMPS_IN_SCAN = 4,
    JPGD_MAX_BLOCKS_PER_ROW = 8192,
    JPGD_MAX_HEIGHT = 16384,
    JPGD_MAX_WIDTH = 16384
};

typedef int16 jpgd_quant_t;
typedef int16 jpgd_block_t;

class jpeg_decoder
{
public:
    // Call get_error_code() after constructing to determine if the stream is valid or not. You may call the
    // get_width(), get_height(), etc. methods after the constructor is called. You may then either destruct the object,
    // or begin decoding the image by calling begin_decoding(), then decode() on each scanline.
    jpeg_decoder(jpeg_decoder_stream *pStream);

    ~jpeg_decoder();

    // Call this method after constructing the object to begin decompression.
    // If JPGD_SUCCESS is returned you may then call decode() on each scanline.
    int begin_decoding();

    // Returns the next scan line.
    // For grayscale images, pScan_line will point to a buffer containing 8-bit pixels (get_bytes_per_pixel() will
    // return 1). Otherwise, it will always point to a buffer containing 32-bit RGBA pixels (A will always be 255, and
    // get_bytes_per_pixel() will return 4). Returns JPGD_SUCCESS if a scan line has been returned. Returns JPGD_DONE if
    // all scan lines have been returned. Returns JPGD_FAILED if an error occurred. Call get_error_code() for a more
    // info.
    int decode(const void **pScan_line, uint *pScan_line_len);

    inline jpgd_status get_error_code() const { return m_error_code; }

    inline int get_width() const { return m_image_x_size; }
    inline int get_height() const { return m_image_y_size; }

    inline int get_num_components() const { return m_comps_in_frame; }

    inline int get_bytes_per_pixel() const { return m_dest_bytes_per_pixel; }
    inline int get_bytes_per_scan_line() const { return m_image_x_size * get_bytes_per_pixel(); }

    // Returns the total number of bytes actually consumed by the decoder (which should equal the actual size of the
    // JPEG file).
    inline int get_total_bytes_read() const { return m_total_bytes_read; }

private:
    jpeg_decoder(const jpeg_decoder &);
    jpeg_decoder &operator=(const jpeg_decoder &);

    typedef void (*pDecode_block_func)(jpeg_decoder *, int, int, int);

    struct huff_tables
    {
        bool ac_table;
        uint look_up[256];
        uint look_up2[256];
        uint8 code_size[256];
        uint tree[512];
    };

    struct coeff_buf
    {
        uint8 *pData;
        int block_num_x, block_num_y;
        int block_len_x, block_len_y;
        int block_size;
    };

    struct mem_block
    {
        mem_block *m_pNext;
        size_t m_used_count;
        size_t m_size;
        char m_data[1];
    };

    jmp_buf m_jmp_state;
    mem_block *m_pMem_blocks;
    int m_image_x_size;
    int m_image_y_size;
    jpeg_decoder_stream *m_pStream;
    int m_progressive_flag;
    uint8 m_huff_ac[JPGD_MAX_HUFF_TABLES];
    uint8 *m_huff_num[JPGD_MAX_HUFF_TABLES];      // pointer to number of Huffman codes per bit size
    uint8 *m_huff_val[JPGD_MAX_HUFF_TABLES];      // pointer to Huffman codes per bit size
    jpgd_quant_t *m_quant[JPGD_MAX_QUANT_TABLES]; // pointer to quantization tables
    int m_scan_type;                        // Gray, Yh1v1, Yh1v2, Yh2v1, Yh2v2 (CMYK111, CMYK4114 no longer supported)
    int m_comps_in_frame;                   // # of components in frame
    int m_comp_h_samp[JPGD_MAX_COMPONENTS]; // component's horizontal sampling factor
    int m_comp_v_samp[JPGD_MAX_COMPONENTS]; // component's vertical sampling factor
    int m_comp_quant[JPGD_MAX_COMPONENTS];  // component's quantization table selector
    int m_comp_ident[JPGD_MAX_COMPONENTS];  // component's ID
    int m_comp_h_blocks[JPGD_MAX_COMPONENTS];
    int m_comp_v_blocks[JPGD_MAX_COMPONENTS];
    int m_comps_in_scan;                     // # of components in scan
    int m_comp_list[JPGD_MAX_COMPS_IN_SCAN]; // components in this scan
    int m_comp_dc_tab[JPGD_MAX_COMPONENTS];  // component's DC Huffman coding table selector
    int m_comp_ac_tab[JPGD_MAX_COMPONENTS];  // component's AC Huffman coding table selector
    int m_spectral_start;                    // spectral selection start
    int m_spectral_end;                      // spectral selection end
    int m_successive_low;                    // successive approximation low
    int m_successive_high;                   // successive approximation high
    int m_max_mcu_x_size;                    // MCU's max. X size in pixels
    int m_max_mcu_y_size;                    // MCU's max. Y size in pixels
    int m_blocks_per_mcu;
    int m_max_blocks_per_row;
    int m_mcus_per_row, m_mcus_per_col;
    int m_mcu_org[JPGD_MAX_BLOCKS_PER_MCU];
    int m_total_lines_left; // total # lines left in image
    int m_mcu_lines_left;   // total # lines left in this MCU
    int m_real_dest_bytes_per_scan_line;
    int m_dest_bytes_per_scan_line; // rounded up
    int m_dest_bytes_per_pixel;     // 4 (RGB) or 1 (Y)
    huff_tables *m_pHuff_tabs[JPGD_MAX_HUFF_TABLES];
    coeff_buf *m_dc_coeffs[JPGD_MAX_COMPONENTS];
    coeff_buf *m_ac_coeffs[JPGD_MAX_COMPONENTS];
    int m_eob_run;
    int m_block_y_mcu[JPGD_MAX_COMPONENTS];
    uint8 *m_pIn_buf_ofs;
    int m_in_buf_left;
    int m_tem_flag;
    bool m_eof_flag;
    uint8 m_in_buf_pad_start[128];
    uint8 m_in_buf[JPGD_IN_BUF_SIZE + 128];
    uint8 m_in_buf_pad_end[128];
    int m_bits_left;
    uint m_bit_buf;
    int m_restart_interval;
    int m_restarts_left;
    int m_next_restart_num;
    int m_max_mcus_per_row;
    int m_max_blocks_per_mcu;
    int m_expanded_blocks_per_mcu;
    int m_expanded_blocks_per_row;
    int m_expanded_blocks_per_component;
    bool m_freq_domain_chroma_upsample;
    int m_max_mcus_per_col;
    uint m_last_dc_val[JPGD_MAX_COMPONENTS];
    jpgd_block_t *m_pMCU_coefficients;
    int m_mcu_block_max_zag[JPGD_MAX_BLOCKS_PER_MCU];
    uint8 *m_pSample_buf;
    int m_crr[256];
    int m_cbb[256];
    int m_crg[256];
    int m_cbg[256];
    uint8 *m_pScan_line_0;
    uint8 *m_pScan_line_1;
    jpgd_status m_error_code;
    bool m_ready_flag;
    int m_total_bytes_read;

    void free_all_blocks();
    JPGD_NORETURN void stop_decoding(jpgd_status status);
    void *alloc(size_t n, bool zero = false);
    void word_clear(void *p, uint16 c, uint n);
    void prep_in_buffer();
    void read_dht_marker();
    void read_dqt_marker();
    void read_sof_marker();
    void skip_variable_marker();
    void read_dri_marker();
    void read_sos_marker();
    int next_marker();
    int process_markers();
    void locate_soi_marker();
    void locate_sof_marker();
    int locate_sos_marker();
    void init(jpeg_decoder_stream *pStream);
    void create_look_ups();
    void fix_in_buffer();
    void transform_mcu(int mcu_row);
    void transform_mcu_expand(int mcu_row);
    coeff_buf *coeff_buf_open(int block_num_x, int block_num_y, int block_len_x, int block_len_y);
    inline jpgd_block_t *coeff_buf_getp(coeff_buf *cb, int block_x, int block_y);
    void load_next_row();
    void decode_next_row();
    void make_huff_table(int index, huff_tables *pH);
    void check_quant_tables();
    void check_huff_tables();
    void calc_mcu_block_order();
    int init_scan();
    void init_frame();
    void process_restart();
    void decode_scan(pDecode_block_func decode_block_func);
    void init_progressive();
    void init_sequential();
    void decode_start();
    void decode_init(jpeg_decoder_stream *pStream);
    void H2V2Convert();
    void H2V1Convert();
    void H1V2Convert();
    void H1V1Convert();
    void gray_convert();
    void expanded_convert();
    void find_eoi();
    inline uint get_char();
    inline uint get_char(bool *pPadding_flag);
    inline void stuff_char(uint8 q);
    inline uint8 get_octet();
    inline uint get_bits(int num_bits);
    inline uint get_bits_no_markers(int numbits);
    inline int huff_decode(huff_tables *pH);
    inline int huff_decode(huff_tables *pH, int &extrabits);
    static inline uint8 clamp(int i);
    static void decode_block_dc_first(jpeg_decoder *pD, int component_id, int block_x, int block_y);
    static void decode_block_dc_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y);
    static void decode_block_ac_first(jpeg_decoder *pD, int component_id, int block_x, int block_y);
    static void decode_block_ac_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y);
};

} // namespace jpgd

#endif // JPEG_DECODER_H
